1. Field of the Invention
The present invention relates generally to an antenna provided in a mobile communication terminal to transmit and receive radio signals and, more particularly, to a broadband internal antenna provided in a mobile communication terminal to process broadband signals.
2. Description of the Related Art
Currently, mobile communication terminals are required to provide various services as well as be miniaturized and lightweight. To meet such requirements, internal circuits and components adopted in the mobile communication terminals trend not only toward multi-functionality but also toward miniaturization. Such a trend is also applied to an antenna, which is one of the main components of a mobile communication terminal.
FIG. 1 is a view showing the construction of a general Planar Inverted-F Antenna (PIFA).
The PIFA is an antenna that can be mounted in a mobile terminal. As shown in FIG. 1, the PIFA basically includes a planar radiation part 2, a short pin 4 connected to the planar radiation part 2, a coaxial line 5 and a ground plate 9. The radiation part 2 is fed with power through the coaxial line 5, and forms impedance matching by short-circuiting the ground plate 9 using the short pin 4. The PIFA must be designed in consideration of the length L of the radiation part 2 and the height H of the antenna according to the width Wp of the short pin 4 and the width W of the radiation part 2.
Such a PIFA has the directivity that not only improves Synthetic Aperture Radar (SAR) characteristics by attenuating a beam (directed to a human body) in such a way that one of all the beams (generated by current induced to the radiation part 2), which is directed to the ground, is induced again, but also enhances a beam induced to the direction of the radiation part 2. Furthermore, the PIFA acts as a rectangular microstrip antenna, with the length of the rectangular, planar radiation part 2 being reduced by half, thus implementing a low-profile structure. Furthermore, the PIFA is an internal antenna that is mounted in a terminal, so that the appearance of the terminal can be designed beautifully and the terminal has a characteristic of being invulnerable to external impact. Such a PIFA is improved in conformity with the multi-functionality trend. Of PIFAs, a multi-band antenna is used as shown in FIG. 2.
FIG. 2 is a view showing a conventional internal dual band antenna.
Referring to FIG. 2, the conventional internal dual band antenna includes a radiation part 20, a power feeding pin 25, and a ground pin 26. The radiation part 20 of the conventional internal antenna includes a high band radiation part 21 placed at the center of the radiation part 20 to process high band signals, and low band radiation parts 22 to 24 spaced apart from the high band radiation part 21 by a certain distance along the periphery of the high band radiation part 21 to process low band signals. That is, the high band radiation part 21 and the low band radiation parts 22 to 24 are connected parallel to each other. Furthermore, the power feeding pin 25 and the ground pin 26 are connected to one end of the radiation part 20.
However, the conventional internal dual band antenna is constructed in such a way that all the radiation parts are formed on a single plane, so that the size thereof is large and the unit cost thereof is high, thus deteriorating the competitive power of recent mobile communication terminals.
FIG. 3 is a view showing a conventional ceramic chip antenna.
Referring to FIG. 3, in the conventional ceramic chip antenna, conductors 34 and 36 performing radiation are formed using a chip stacking process. Although the case where the conductors 34 and 36 are formed in a spiral coil shape is shown in FIG. 3, various modifications are possible. The conductors 34 and 36 are formed of horizontal strip lines 34 printed parallel to a bottom 32, and vertical strip lines 36 formed by filling conductive paste in via holes formed to be vertical to the bottom 32.
Such a conventional ceramic chip antenna 30 can be manufactured in a small size, and has desired efficiency. However, the conventional ceramic chip antenna 30 is problematic in that it is sensitive to external factors because it has a narrow bandwidth, and it is difficult to be applied to an actual mobile terminal because the manufacturing cost thereof is high.